Improved ball milling method for the synthesis of nanocrystalline TiFe compound ready to absorb hydrogen. (13th January 2020)

• Record Type: Journal Article
• Authors: Vega, L.E.R.; Leiva, D.R.; Leal Neto, R.M.; Silva, W.B.; Silva, R.A.; Ishikawa, T.T.; Kiminami, C.S.; Botta, W.J.
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 3(2020)
• Page Start: 2084
• Page End: 2093
• Publication Date: 2020-01-13
• Subjects: Mechanical alloying -- Ball milling -- Hydrogen storage -- TiFe -- Hydrides -- Activation; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2019.11.035
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: In this study, we propose a method to produce nanocrystalline TiFe powder by high-energy ball milling, in order to avoid the common sticking problem of the material to the milling tools, assuring a material prompt to absorb hydrogen as well. The method consists of making a preliminary milling operation with the elemental powders (50:50 stoichiometric ratio) to form a strong adhered layer of the milled material on the surfaces of the vial and balls. The main milling operation is then performed with a new powder charge (same composition as before), but now adding a process control agent (stearic acid). Various processing times - 2, 6, 10 and 20 h - were used in the milling experiments. Nanocrystalline TiFe was synthesized in this way with low oxygen contamination, full yields for milling times of 6 h or over, requiring no heat treatments for the first hydrogen absorption. Hydrogen storage capacity of 1.0 wt% at room temperature under 20 bar was attained by the sample milled for 6 h. Kinetic data from samples milled for 2 h and 6 h agreed with Jander model for the rate limiting step of the hydriding reaction, which is based on diffusion with constant interface area. Highlights: As-milled TiFe absorbs hydrogen at room temperature requiring no thermal activation. High yields were obtained by preparing the media surfaces previously. Mechanical alloyed TiFe milled for 6 h absorbed 1 wt% of hydrogen at 20 bar. Jander model best fits the first hydrogenation of samples milled for 2 h and 6 h.